The objective of this project is to develop an innovative, accurate, and low-cost technology for bedside continuous (vs. intermittent) monitoring of endotracheal tube (ETT) positioning. The new ETT malposition detector (ET-MD) uses automated analysis of breath sounds and will be able to detect bronchial intubation and extubation (tube slippage into the bronchus or out of the trachea, respectively). Broncheal intubation may occur due to tube manipulation or patient movement and may lead to significant hypoxia and atelectasis (and possibly barotrauma and pneumothorax of the ventilated lung). Although extubation may become clinically apparent after some time, instant recognition can help avoid hypoxia. The ET-MD operation exploits the physics principle of the dependence of breath sounds on lung ventilation. There are two essential ET-MD components: 1) Acoustic sensors and 2) Computational and display module that analyzes acoustic signals and reports relevant metrics indicative of ETT location. We propose to construct and test a prototype under likely use conditions. Here, effects of room noise, adventitious sounds, and sensor positioning errors will be investigated in animals. In addition, the device will be tested in human subjects with and without pulmonary conditions and obesity. Key words: (8 maximum) Acoustics, endotracheal tube, intubation, malpositioning, breath sounds, diagnosis.